Flash welder control



Jan. 5, 1954 H. H. HANSEN 2,665,360

FLASH WELDER CONTROL Filed March 14, 1952 3 Sheets-Sheet l z [i INVENTORl); v H ANs H. HANSEN IT In ATTORNEY Jan. 5, 1954 H, H, HANSEN 2,665,36@

FLASH WELDER CONTROL Filed March 14, 1952 5 Sheets-Sheet 9 QI!- l2 I3 II4 o 37 42 I7 #E Z 35 F I9 INVENTOR l-E 3 HANS H. HANSEN ATTORNEY Jan.5, E954# H. H. HANSEN FLASH WELDER CONTROL Filed March 141, 1952 5Sheets-Sheet 3 INVENTOR HANS H. HANSEN ATTORNEY Patented Jan. 5, 1954UNITED STATES PATENT OFFICE FLASH WELDER CONTROL Hans Henning Hansen,Warren, Ohio, assignor to The Taylor-Winfield Corporation, Warren, Ohio,a corporation of 0hio Application March 14, 1952, Serial No. 276,544

16 Claims. l

This invention relates to electric resistance welding apparatus and moreparticularly to an improved system for controlling the movement of amovable work-holding platen in a flash-butt welding machine. The manyoperational and control requirements, in a practical flash-butt Welder,such as the smooth uninterrupted advance of the work-holding platenduring a welding cycle, control of the time-position pattern Changes inthe character of the welds to be effected or in the metal sections beingwelded require one or more adjustments to be made in the above detailedoperational sequence of the machine and it is now within the Weldingmachine operators skill to specify a predetermined schedule for theparticular kind of Work at hand. Thus, for example, in resetting themachine a new job may require merely that f Such advance, andadjustments Of the d- 10 the extent of burn-ofi should be increasedmensions of flashing movement, upset movement, while all otheradjustments remain xed. It is and final die opening, in scheduling themachine accordingly desirable that adjustment of any for particularwelding operations, has always one factor may be effected Withoutdisturbing presented a difficult control problem. While a other pre-setfactors and it is another object substantial number of systems haveheretofore l5 of the invention to provide a control system been proposedand used in so functioning welders for the purpose stated in whichindividual adof this type that acceptable welds are obtained justment ofthe various Welding schedule factors 0n various types of Work, Suchsystems have may be quickly and easily made without rethe disadvantagethat their adjustment and realigning the entire control or other partsthereadjustment is a difficult and time-consuming of. Thischaracteristic is particularly advantask or are deficient in providingfor beneicial tageous as regards the control of movement of variation inone or more operating characterthe platen during flashing wherein it iscomistics when setting up a particular machine for monly desirable toaccelerate the movement of a new job. the platen toward the end of theflashing period. It is accordingly the primary object of the It hasheretofore been proposed to utilize a present invention to provide animproved conspeed-control cam for this purpose and I also trol systemfor governing the movement of a utilize the same in my present inventionbut movable work-holding platen in an electric rethe same is sointegrated with other components sistance ash-buttwelder which whilepossessing of the control system that the same general Comprehensive andCOmDlete adiustablty 0f 30 optimum pattern of movement may be obtainedall the operational factors which predetermine from the same cam andcontrol mechanism even the performance of a particular machine for athough the average rate of advance of the movparticular job isnevertheless entirely practical able platen is increased or decreasedand/or even and economical by reason of the employment of though achange is made in the length of flashing areduced number of principalcomponents which or burn-off movement of the platen. For in themselvesare of rugged and durable nature, practically all ranges of work thesame cam and of the use of a minimum number of points may be employed.of adjustment which are conveniently grouped A further object of theinvention is the profor ease of manipulation by the machine opvision ofimproved control apparatus having the erator. The adjustments providedfor include features of adjustability outlined above in which thevnormal retracted position of the movable the adjustments are effectiveon rugged complaten (which determines also the extent of ponents thuseliminating any possibility of darnburn-off of the work pieces), thetime-position age due to rough handling and in which the pattern ofmovement of the platen both during adjustments when once made willremain rigidly flashing and upsetting of the work, the dimenfixed overprolonged severe conditions of servsional extent of upset of the Work,and the miniice whereby substantially improved consistency mum or finaldistance between the fixed and in the carrying out of the weldingschedule may movable work-holding and current-conducting be obtained.dies of the machine, commonly termed final Yet another object of theinvention is the die opening. As is well understood in this artprovision in control apparatus having the feathe movable platen shouldadvance smoothly tures and advantages outlined above of arrangeaccordingto a predetermined time-position patments whereby the cycle of movementof the tern during the flashing phase of the welding platen during awelding operation may be dicycle and at upset the movable platen shouldrected either entirely automatically, entirely advance much more rapidlyyet under firm con- 5 5 manually, or combined automatically and mantrolto thus join the metal to be welded.v

nally. Further, such cycle of movement may include accurate control overthe extent or dimension of platen retraction (die opening) at thecompletion of the successive welding cycles and unclamping of the workin order that such initial opening may be limited as required todischarge the welded work piece from the machine. it may also include aninitial quick closing of the dies under a controlled lower pressure forpreheating the work pieces by the flow of current from the weldingtransformer preparatory to the initiation of the flashing period of thewelding cycle as is desirable in some classes of work.

The above and other objects and advantages of the invention will becomeapparent upon consideration of the following specication andaccompanying drawing wherein there is disclosed a preferred embodimentof the invention.

In the drawing:

Figure 1 is a schematic representation of a flash Welder control `systemembodying the principles of my invention with parts positioned to startthe upset of the work upon completion of the ashing stage in the weldingcycle;

Figure 2 is a fragmentary showing of the ap- -paratus of Figure 1,with'the parts positioned to initiate dashing of the work under handcontrol as may sometimes be desired at the initiation of a weldingcycle;

Figure 3 shows the apparatus of Figure 1 but with the parts positionedto initiate flashing of the work under automatic control;

Figure 4 shows the apparatus of Figures 2 and 3 with the partspositioned at the end of upset of the work; and

Figure 5 is a detailed sectional View, on an enlarged scale, of aportion of the mechanical apparatus of the assemled control of Figure 1.

Referring first to Figure l, the Hash welding machine proper is shownschematically as comprising a welding transformer I9 the two secondaryterminals of which are yconnected respectively to a fixed work-holdingplaten Il and a movable platen I2, the latter of which is arranged to beactuated by a double acting hydraulic cylinder I3, the piston rod I4 ofwhich extends outwardly of either end of the cylin der. The primarywinding of welding tra-nsformer I is energized from a suitable currentsource through a control panel l which includes, among otherinstrumentalities, a timer (not shown) which is operative to interruptthe flow of current a predetermined interval following the closure of aswitch IE, the function of which will be explained below. Thetime-position pattern of movement imparted to the movable platen I2 withwhich the present invention is primarily concerned is determined, ofcourse, by the flow of oil into the opposite endsr of the cylinder I3and such flow is controlled by a follow valve I1 and a dumping valve I8,the latter being utilized only during upset of the work pieces torapidly supply a large volume of oil under high pressure to the outerend of cylinder I3 to effect a quick forward movement or the movableplaten I2, all in accordance with usual practice in the art.

Follow valve Il is preferably a sliding spool type of valve, as shown,operated by the rod I9 which in the vertical position shown is operativeupon upward movement to valve oil under pressure from a source Z throughconduit 2I to the inner end of cylinder I3 while exhaustmg oil from theouter end of the cylinder through conduit 22 and outlet port 23.Conversely, upon downward movement of rod I9 oil is admitted to theouter end of cylinder I3 to effect an inward or advance movement of theplaten l2. Through linkage now to be described the sliding movement ofrod IQ is differentially controlled by either an automatic or manualfactor balanced against the. factor of movement of the platen I2 assensed through the outward projecting end of the connected piston rodI4. Thus, the outer end of rod I9 is pivotally connected at 24 to anintermediate portion of a lever 25, one end of which is provided with acam-following roller 26 maintained in contact with a cam 21 by spring28. Spring 28 encircles the shank of a slidably mounted guide stem 29which is pivotally connected to the lever 25 as shown. The opposite endof lever 25 is slotted longitudinally and provided with ra f1tting 30which serves to pivotally connect lever 25 with a similarly slotted endportion of a second lever 3| which is pivotally mounted intermediate itsends on a carrier 32. Fitting 39 is so constructed that it may bepositioned and secured at a preselected position longitudinally lalongthe slotted ends of the levers 25 and 3l whereby the drive ratio betweenthese levers may be varied as desired. Carrier 32 is a bellcrank type oflever pivotally carried on a iixed part of the welding machine at 33.Also pivotally carried on a fixed part of the welding machine is a handcontrol lever 34 which has driving connection with carrier 33 throughconnecting link 35. The end of lever 3l opposite the slotted end thereofis mechanically coupled by means of a link 36 with a bellcrank lever 3'1which has the outer end of its driving leg received in an annular groove33 of a driving sleeve 39.

Referring now more particularly to Figures 1 and 5 it should be notedthat the sleeve 39 is mounted on the piston rod I4 of the principalplaten drive cylinder I3 and has at its outer end a radially outwardextending iiange 4u which is received within the internalcircumferential groove 4I of a nut assembly 42 which is screw threadedlyreceived on a screw threaded outer portion of the rod I4. Nut assembly42 is comprised of a body member 43 having both internal and externalthreads and an outer flange 44. Screw threaded on the external threadsof the body member 43 is rst a locking nut 45 and then a sleeve 4Shaving an internal shoulder at its inner end to form the groove 4I. Itshould be observed that the axial length of the groove 4I is adjustableand normally greater than the Iaxial length of the ange 40 of the drivesleeve 39 so that the drive sleeve 39 may have limited sliding movementon the rod I 4 relative to the nut vassembly 42 and to facilitate suchsliding movement a sleeve type of bearing 4l may be interposed betweenthe internal diameter of the sleeve 39 and a smooth portion of theprojecting rod I 4. To normally bias the drive sleeve 39 to extendedposition relative to the body member 43' of the nut assembly 42 thisbody member is formed intermediate its inner and outer threads with -aplurality of circumferentially spaced but axially extending bores 48 toslidably receive hollow guide pins 49 the closed outer ends of whichbear against the face of the flange 49. Also received within the bores48 and partially within the pins 43 are the compression springs 50 whichbias the pins 49 outwardly thereby yieldably holding the drive sleeve 3Sextended position as described.

The above described relative sliding movement between the drive sleeve39 and the nut assembly 42 represents and controls the extent of upsetmovement of the movable platen of the welding machine and it should benoted that the extent or dimension of this upset movement may be readilyadjusted by backing off the locking nut 45 from the sleeve 46 afterwhich this sleeve may be rotated on the external threads of the bodymember 43 to vary the axial length of the internal groove 4|. As willappear later, it is the absolute position of the drive sleeve 39relative to the fixed cylinder I 3 which determines the point during thepattern of movement of the platen during the welding cycle at which thedumping valve I8 is actuated to initiate the rapid upset movement.

A large lock nut 5| bears against the outer face of the flange 44 of thebody member 43 of the nut assembly 42 whereby this nut assembly isrigidly locked in selected position on a threaded end portion of thepiston rod I4 and at the very outer extremity of this rod there issecured a stop nut 52.

In the assembled apparatus shown hydraulic fluid pressure is furnishedby a pump 53 the outlet of which is connected through check valve 54,conduit 55, pressure regulator 56 to the inlet. 29 of follow valve I1,and connecting with the conduit 55 is an outlet of pump 53 is connectedto the inlet of dump valve I8 through check valve 58 and a manualregulator valve 59 and, again, an accumulator (6U) is arranged in thehydraulic circuit to furnish a large volume of high fluid in a shortperiod of time as is required for effective upsetting movement of theplaten in the Weldingr machine.

Control cam 21 is arranged to be actuated by an electric motor 6I whichis energized from a suitable power source through suitable relay controlapparatus 62 having associated therewith an initiating switch 63, areset switch 64, and a limit switch 65. Switch 63 is arranged to beclosed upon the control lever 34 being moved far to the left, as viewedin Figure 1, while switch 64 is arranged to be closed upon lever 34being moved far to the right as viewed in this figure. Switch 65 issynchronized with the cam 21 to be actuated upon the cam reaching itsproper initial starting position at the beginning of a switch 64, motor6I and cam 21 are reversed to return the cam to its proper initialstarting position whereupon switch 65 acting through the relay control62 deenergizes motor 6I thus readying the apparatus for the nextsucceeding-cycle of operation. Upon closure of switch 63 to initiate thewelding cycle motor 6I is energized in a forward direction to drive cam21 at a proper speed through suitable gearing, not shown.

Switch i6 is arranged to be closed by link 36 upon driving sleeve 39reaching a predetermined position-normally upon this sleeve contactingthe outer face of the outer end housing of cylinder I3, and mechanicallyganged with switch I6 is a switch 66 which controls the energization ofa solenoid 61 for actuating the dump valve I3 whereby the dumping valveis actuated upon the sleeve 39 reaching the above specified position.

In normal repetitive operation of the welding machine the pattern ofmovement of the-movaccumulator 51. Likewise, the

pressure 53- extent or dimension of fly prevented. As explained above,

able platen will be automatically controlled and in such case the manualcontrol lever 34 will remain in the position shown in Figure 1, beingheld in such position by a spring-pressed pawl 63 engaging a notch inlink 35. When the manual control lever is so positioned and locked thecarrier 32 is firmly seated on a fixed anvil 69 whereby the supportingfulcrum for the lever 3l is firmly fixed. Now by referring to Figure 3which shows the position of the parts at the start of a welding cycleunder automatic control (the closure of switch 63 having started thetimed rotation of cam 21) lever 25 first begins to rock downwardly aboutthe pivot point provided by fitting 30 and the core of follow valve I1moves downwardly to admit fluid pressure to the outer end of cylinderI3. Such admission of fluid pressure continues until the resultantactuation and extent of movement of the rod I4 and movable platen I2acting through lever 31, link 36 and lever of fitting 30 sufficiently tocompensate for the downward component effected by cam 21 whereby thevalve I1 is throttled, and in this manner the pattern of movement of themovable platen I2 is accurately controlled by the contour of the cam 21,particularly since cam 21 is rotated at a controlled speed. As explainedabove, the ratio of advantage between the levers 25 and 3| is controlledby the longitudinal position of the iitting 30 along these levers. Withthe fitting to the left as shown in Figure 3 slight deviation in the cam21 will result in maximum deviation in the rod I4 and it may be saidtherefore that the parts in Figure 3 are adjusted for maximum burn-offdimension, it being understood that the operating radius of cam 211 isminimum at the start of a Welding cycle. By moving the fitting 30 to theright, as viewed in Figure 3, the extent of burn-oil? during theflashing period may be diminished as required in the particular weldingjob at hand. It will become clear later that this burn-oli dimension maybe adjusted entirely independently of all the other settings of thecomplete apparatus ment, timing of upset current.

The flashing movement initiated by movement of the parts to the positionshown in Figure 3 continues until the same is interrupted by the startof the rapid upset movement which is initiated upon the parts reachingthe positions shown in Figure 1. Here the cam 21 has eiected suchclosing movement of the piston rod I4 that the driving sleeve has comeinto contact with the cylinder I3 and the link 36 has closed switches I6and 66. Immediately the dumping valve I8 is actuatedy far outstrippingthe follow valve I1 and the movable platen I2 is surged forwardly toimpart to the work pieces being welded the rapid advance under heavyforce normally required to effect dense solid welds. However, ifuncontrolled, such quick upsetting movement may well result in excessiveand unnecessary deformation of the work pieces or cracking of the weldand in my apparatus I accordingly control the rate of advance of themovable platen during upset by means of the throttle valve 59 and thethis upsetting movement by means of the nut assembly 42, the bodyVinember 43 of which closes the drive sleeve 39 movement of the rod I 4and platen 3i raises the pivot point` onto the adjacent end of` wherebyfurther forward I 2 is absolutethe extent ofi this upsetting movementmay be .decreased-,by

shortening the Yaxial length of vgroove All, it being `understood thatthe operator for switch 'tt 'is so adjusted that the switch is closedjust as the :sleeve 39 .contacts cylinder I3 and while the flange handle34, is actuated or moved during the quick 'upsetting movement of theplaten of the welding machine, thus reducing the strain and wear onthese precision parts and eliminating all tern 'dency of these parts toget out of adjustment due Ato the shock of the upsetting movement.

.- Gne of the adjustments mentioned above as being desirable in theoperation of a flash Welding machine is the so called iinal diedimension which is the-spacing between the workheld and currentconducting dies on the fixed and movable platens at the completionof'upset and in accordance with the-teachings o-my invention adjustmentof the iinal die dimension may be readily accomplished simply byback-ing on? the locked nut l and rotating the nut rassembly .42' on thethreaded rod is in either direction. If the nut assembly s2 is screwedoutwardly 'the nal die dimension is less and fit should be particularlynoted that the change in this dimension does not change or eifeet thepreviously set upset dimension, the extent of burn-oli, or any of theother settings of the assembled control apparatus.

VIn actual practice a variable speed drive is interposed between themotor El and the cam 21. so 'that the cam 2l may be rotated at variablespeed to change the rate of advance of the mov able platen of thewelding machine during flashing without effecting any of theother'adjust-` ments of the control. Normally, the rate oraccelerationof the movable platen during flashing is the same for allwork on any particular ma'- chine and consequently the same cam Elmay beused for widely varying jobs but, if desired, the cam 21 may be readilyinterchanged with other cams having different contours.

At the completion of a Welding cycle the work holding clamps are firstreleased, aiter which the welded work may be removed and the desopenedPreparatory to receiving the next 'work to 'be welded. The dies may beopened by swinging control lever 34 far -to the right, as viewed inFigure 1, whereby the levers 3| and 25 are swung far upwardly to raisethe core in follow valve Il whereby uid pressure at large volume fromthe accumulator l5i' is admitted to the platen end of cylinder I3 torapidly retract platen l2.- However, itis-often necessary due to shapefactors ofthe work pieces that the vdies be opened only a .verysmall-controlled distance to permit removal of the work-after release ofthe clamps and it is most desirable that the control of the dimension ofthis initial die retraction be eiected by the master control lever 34either by moving the same (to the right as viewed in Figure l) to avisually determined position or against a retractible stop, not shown.By reason oi the above explained independence of the upset movementcontrol with respect to the control lever 3d no dimensional control overthe opening oi the dies during an initial range equal to the upsetdimension can be eiected bythe control lever 3s in the apparatus thusfarA described. -To overcome this problem i pr 'de the latchingarrangementshown in detal Figure 5 wherein. a latching lever 10 ispivotally mounted at vH on the control drive sleeve -39 and has at itsouter end a hook 'i2 which is arranged to snap over the outer end -ofthe flange 44 of the upset nut assembly 42 when the nut and drive sleeveare collapsed at the cornpletion of upset as explained. A coil spring i3retains the lever 'l0 in latching position as a control sleeve 39 backsaway from the cylinder VI3 at the l start of retracted movement of theplaten l2. By thus locking the drive sleeve 39 and nut 42 together withthe upset dimension removed from the linkage it should be understoodthat all of the retraction movement of the platen l2 is under theprecise-control of the manual lever SA which,

as explained above, may be either visually positioned or brought againsta stop to accurately limit the dimension of the initial retraction ofthe dies preparatory to the removal of the welded work. Upon suchremoval, however, thedies may be retracted their full extent byfurther'- movement oi the control lever 3s to the rig-ht and as theirfull open position is reachedacamsurface 'id on vthe opposite end oflever 'it engages a projection l5 cantilevered on the cylinder i3'v itis rotated to release theV whereby the lever latching hook 'l2 andimmediately the springs 5G in the nut i2 act to expand the nut 3S andspring ft2 whereupon the upset dimension is reestablished in the controllinkage preparatory to the next succeeding cycle of operation of theWelding machine. If the function of the latch i0 is not required in theoperation ofthe Welding machine on a particular job the same may bereadily removed from the control sequence simply lby tightening down ascrew 'It which retains the lever i@ in elevated or non-latchingposition, s

At the end of upset and completion of the weld the control parts arepositioned asvshown in Figure 4 and, as explained above, at this timethe work clamps are released and the welded work removed and by movingthe control lever 34 iar to theright to fully retract the dies asexplained above the control parts assume the position shown in Figure 2.This is the starting position for manual control of the movable platenduring the ilashing phase of the Welding cycle. lt should be understood,of course, that in some operations the flashing is under full automaticcontrol in which case the work pieces are set further apart so that theyjust come together upon the control linkage being moved to the-po'sitions shown in Figure 3 which, as stated above, represents the startof automatic dashing. Ii manual control is to be used at the start ofashing (for pre-heating or for burning off of large irregularities) thework pieces are positionedcloser together so that they may beAmanipulated into and out of engagement Awith each other under manualcontrol .of levers't within .the .range of movement' outside the 'closL-ing` of switch t3. For full 'manual operation the energy source formotor tl may be entirely .disconnected and the cam 2'! moved'to andretained in a manual position which is such as to'per' mit full manualcontrol of the flash movement of platen l2 by means lof leverS down to.fthe point of upset which, as stated above, Vis reached when the drivesleeve 39 engages cylinder i3.' It should now be apparent that'l 'haveprovided an improved flash welder control 'which accomplishes theobjects initially set out'above. While the apparatus of thiscontrol-'requires but a reduced number of component parts, as com'-pared to ilash Welder controls of comparable functioning heretoforeproposed, the- :parts g are relatively simple in construction andreadily adaptable to rugged design to thereby render long and dependableservice even under severe conditions of industrial usage. Of substantialimportance are the features that adjustments may be made in any one of alarge number of operational characteristics Without impairing theadjustment of the other settings, that the precision follow valve andcontrol linkage therefor is eifectively shielded from shock during theupsetting phase of the welding cycles, and that it is possible to effectan accurately controlled but limited initial opening movement of thedies to permit special work to be readily removed therefrom withoutdanger of injury to the work or to the dies.

Having thus described my invention what I claim is new and desire tosecure by Letters Patent is:

l. In an electric resistance flash-butt welder having a movablework-holding platen and a hydraulic cylinder for moving said platen thecombination of a rod secured to and movable with said platen, astationary abutment through which said rod extends, a nutscrew-threadedly received on said rod on the opposite abutment from saidplaten, a drive sleeve slidably received on said rod intermediate saidabutment and said nut and interlocked with said nut to have limitedaxial movement with respect to said nut, yieldable means normallyretaining said sleeve in outward position with respect to said nut, afollow valve for controlling the now of fluid to said cylinder, a cam,means to move said cam at a predetermined speed, means to actuate saidfollow valve comprising dilferential linkage interconnecting said sleeveand said cam and having an intermediate member connected to said valvewhereby fluid is admitted to said cylinder through said valve to effecta predetermined time-position pattern of movement in .Y

said platen as determined by the configuration and speed of movement ofsaid cam, a second valve to supply fluid to said cylinder in a directiontending to move said platen in a forward direction at a rate greaterthan the follow valve, and means operative upon said sleeve reachingsaid abutment during advance movement of said platen to actuate saidsecond valve whereby advance movement of said platen is continuedindependently of subsequent movement of said linkage and follow valve.

2. Apparatus according to claim l further characterized in that themeans interlocking said sleeve and said nut includes means to vary thedimension of the limited relative axial movement between said sleeve andnut.

3. Apparatus according to claim 1 further characterized in that saidsleeve comprises a radially outward directed flange, said nut having aninternal annular groove to receive said flange, and means on said nut tovary the axial length of said groove.

4. Apparatus according to claim l further characterized in that saiddiiferential linkage further includes adjustable means to decrease thedriving ratio between said sleeve and said follow valve while increasingthe driving ratio between said cam and said follow valve and vice Versawhereby the extent of movement of said platen effected by apredetermined movement of said cam during normal operation may bevaried.

5. Apparatus according to claim 1 further characterized in that saiddifferential linkage cornprises a lever pivoted intermediate its endsand having one of its ends connected to said sleeve,

side of said 10 a second lever pivoted intermediate its ends to theoperator for said valve and having one of its ends in contact with saidcam, and means pivotally interconnecting the other ends of said levers.

Apparatus according to claim 5 further including manual means forshifting the pivot point of the rst mentioned lever in a directionparallel with the direction of mov-ement of said operator whereby saidoperator may be moved independently of actuation of said cam and saidsleeve.

T. Apparatus according to claim 6 further including means to latch saidsleeve and nut together upon said sleeve reaching an inward p0- sitionwith respect to said nut upon completion of advance movement of saidplaten resulting from actuation of said second valve, and means torelease said latching means upon said nut and sleeve reaching apredetermined outward position with respect to said abutment duringretracted movement of said platen.

8. In an electric resistance flash-butt Welder having a movablework-holding platen and a hydraulic cylinder for moving said platen aswell as a rod secured to said platen and extending longitudinally of thedirection of movement thereof, an abutment through which said rodextends, a nut screw-threadedly received on said rod on the oppositeside of said abutment from said platen, a drive sleeve slidably receivedon said rod intermediate said abutment and said nut and interlocked withsaid nut to have limited axial movement with respect thereto, yieldablemeans normally retaining said sleeve in outward position with respect tosaid nut, a valve for coniiuid to said cylinder, linkage meansinterconnecting said sleeve and valve for actuating the latter inaccordance with longitudinal movement of the sleeve.

9. Apparatus according to claim 8 further including means independent ofsaid valve to admit fluid pressure to said cylinder whereby forwardmovement of said platen and rod may be continued after stoppage ofmovement of said sleeve by said abutment, means to latch said sleeve andnut together when in closed position during such continued movement ofsaid platen and rod, and means to release said latching means duringoutward travel of said sleeve and nut away from said abutment uponretraction of said platen.

1U. Apparatus according to claim 9 further characterized in that saidmeans to latch comprises a lever pivotally mounted intermediate its endson said sleeve and extending longitudinally of said sleeve and nut andhaving a hook-like end portion adapted to be received over an externalshoulder on said nut upon said nut and sleeve reaching relatively closedpositions, means biasing said lever to latching position, a cam on theopposite end of said lever, and a fixed cam actuator mounted on saidabutment and adapted to tilt said lever to unlatching position uponoutward movement of said sleeve and nut away from said abutment.

1l. In a hydraulic control system for an electric resistance hash-buttWelder having a movfor controlling the iiow of hydraulic fluid underpressure to said cylinder to advance said platen through an initialiiashing range of movement and a second valve to furnish fluid to saidcylinder to advance said platen through a further or "acetico ii upsetrange of movement, differential mechanical linkage for actuating saidfirst mentioned valve, means for actuating said linkage comprising adrive member, yieldable means interconnecting said platen and said drivemember whereby said drive member may move forwardly along with saidplaten over said first range of movement, and stop means to interruptmovement of said drive member during movement of said platen through itssaid further range of movement.

12. Apparatus according to claim 11 further including a cam havingoperative driving relation with said differential linkage, and means tomove said cam at a predetermined speed whereby said first valve iscontrolled to effect a predetermined time-position pattern of movementto said platen duringV said rst range of movement.

13. Apparatus according to claim 12 further including a manual controlmember also connected to said differential linkage whereby movement ofsaid platen may be effected independently of movement of said cam.

14. In an electric resistance flash-butt Welder having a movablework-holding platen and a hydraulic cylinderv for moving said platen thecombination of a rod secured to and movable with vsaid platen,'astationary abutment through which said rod extends, a nutscrew-threade'dly re- Ceived on :said rod and adapted to engage saidabutment to limit the forward advance of said platen, a'follow valve forcontrolling the flow of 'fluid to said cylinder, a cam, means to movesaid cam at a predetermined speed, said valve having a movable core, anddiiferential linkage interconnecting said nut and said cam having amember connected with Vsaid core whereby fluid is admitted to saidcylinder through said valve to effect a predetermined time-positionpattern 4 of movement in said platen as determined by the configurationand speed of movement of said cam.

15. 1n electric resistance flash-butt welding apparatus having a movableplaten and a hydraulic cylinder to move said platen the combination of afollow valveV to control the ow of uid to V'said cylinder, a cam, meansto move said cam at a predetermined speed, and diierentiallinkageinterconnecting said movable platen and said cam and having a memberconnected to the movable member of said valve for operating said valvewhereby said platen may move according to a predetermined time-positionpattern of move- 'ment as determined by the vcortdour and speed ofmovement of said cam.

16. In electric resistance flash-butt welding apparatus having a movableplaten and a hydraulic cylinder for moving said platen the combinationof a follow valve for controlling the flow of fluid into said cylinder,a cam and means to move the same at a predetermined speed, differentiallinkage means interconnecting said platen and said cam with an operatingmember of said valve and operative to control the latter in such mannerthat said platen moves with a time-position pattern as predetermined bythe contour and speed of movement of said cam, said linkage meanscomprising a lever having an extending free end movable in proportion tothe movement of `s aid platen and a second lever of the second classhaving one end pivotally connected to the 'said 'free end of said rstlever at an adjustable position longitudinally thereon and having itsother 'end engaging said cam, Ysaid member being pivotally connected tosaid second class lever intermediate its ends. v'

HANS HENNING HANSEN.

References Cited n the file of this patent UNITED STATES PATENTS NumberName Date 1,892,208 Ferris Dec. 27, 1932 2,373,226 Coates Apr. 1G, 1945

